The Folks That Live on the Hill deals with the functioning of a community. It studies how people form relationships and how they interact. In the novel, the root of the community is the extended "family" that centers on Harry Caldecote, a respected librarian. His immediate family consists of a sister, a brother, the brother's wife, and son. Beyond his blood relationships the concept of family extends to include people like Bunty, who is like a daughter to Harry. Beyond these close relationships lies a circle of friends and lovers who drift in and out of the lives of Harry's family. And beyond these acquaintances are the people who form the backdrop of the community: the tavern owners, barkeeps, taxi drivers, and market owners. These people interact with Harry's family and acquaintances, providing commentary on the principal characters and occasionally playing important roles in the plot, as when the market owners help save a life.
This complex community is the substance of the novel. It shows how people survive by creating complicated webs of love, friendship, and respect with other members of their community. Such webs are seldom perfect, and Amis shows how these relationships can be lost and how people try to compensate for their absence. For instance, Harry has not been able to have a happy marriage. His difficulties with romantic love have led him to become "unusually interested in relations between the sexes." Instead of turning him bitter, his failures at love have made him sympathetic to the emotional needs of others. Although he considers himself a cynical observer of the community, he is actually emotionally involved with the lives that surround him. He cares about people; thus, he is able to explain to Bunty's ex-husband what her lesbianism means. Harry tells him that it is not that she does not care for him. Instead, she cares for him with deep respect; but having sex with him would be like his having sex with a male friend just to please that admired and respected man. This sympathetic attitude toward both Bunty and her husband helps them to heal their wounds and begin to form a strong bond of friendship.
For all its social comedy and criticism, The Folks That Live on the Hill is, at its most fundamental level, a portrait of how people survive emotional crises and the heartaches of everyday life. Even though the character of the community is rapidly changing with the influx of foreign immigrants, the people in it adjust by forming new friendships and new understandings of themselves. At the end of the novel, new alliances are formed as characters seek new ways to survive. This makes Piers's and Fiona's plotting to scare Popsy out of her apartment oddly hopeful; these two dissimilar characters find that they have traits in common, and they act together to help Bunty.